I make mine out of waterproof trousers, two bags to a set of trousers. Roll and glue up the bottom end (20 mm?) of the leg, glue a bit of webbing or similar around the top (just below the top) which is cut off level with the crotch. That length of webbing holds a Fastex buckle piece, one half each side of the leg. To fasten, roll the top of the bag as usual and clip the Fastex buckle.

I've recently bought (on sale) some Hyalite Pneumo dry bags, and I like them a lot.Nylon-type fabric with clear window, and a valve.With the bag packed with clothing and the valve open I can squash the bag 'flat' so it's easy to pack along the hull, then close the valve and it stays flat.For me, a window to show the contents is a big plus when I'm tired.

I use cheap dry bags that are relatively too big. I ain't sure if they work properly as not much goes into a fairly big bag and stored in an air tight compartment (well was, thinking bulk head lost seal). Now I'm looking at my protein powder buckets. They look ideal. Some 8 inch diameter, some 7.5 inch diameter. Water tight thread lid about 5 inch diameter. Not sure if they will drop in or not. Hoping they will. I know the smaller one will. About 4 inch cube (64 cubic inch). That'll work for keys/phone. Note not carrying expedition loads. Guessing bags above them could be used if stuffing required. I basically like decent size threaded plastic jars, they last and they're dry and contents are viewable.